APPLICANT'S ABSTRACT: Tuberculosis is an increasingly serious public health problem, particularly among injection drug users (IDUs). Although isoniazid (INH) chemoprophylaxis treatment for patients infected with tuberculosis is very effective in preventing the development of active disease, medication adherence among IDUs has been poor. The proposed study will test the effectiveness of brief methadone maintenance treatment services of two different intensities, Minimal and Standard, in delivering tuberculosis chemoprophylaxis medication to a cohort of tuberculin skin test (PPD) positive IDUs. The hypothesis is that each of the methadone conditions will be superior to no methadone treatment with respect to completion of chemoprophylaxis, and that Standard will be superior to Minimal methadone services in reducing drug use and AIDS risk behaviors. Subjects will be 90 opioid dependent, PPD positive IDUs with normal chest radiographs, admitted to 21-day methadone detoxification in the San Francisco General Hospital (SFGH) Substance Abuse Services Opiate Detoxification Clinic. After giving informed consent, subjects will be randomly assigned to one of three groups: Standard Methadone Services (SMS), Minimal Methadone Services (MMS), and a Routine Care control group, that will receive no methadone treatment beyond the 21-day detoxification, and will receive only routine referral for tuberculosis (TB) chemoprophylaxis. The SMS and MMS groups will be treated with a six month course of methadone maintenance followed by a one month taper. SMS and MMS subjects will receive a simultaneous course of TB chemoprophylaxis with daily dispensing of INH for six months, on-site through the methadone treatment program. The Routine Care group will receive six months of tuberculosis chemoprophylaxis from the SFGH Tuberculosis Clinic, where they will be seen once per month, evaluated, and given monthly prescriptions for INH. The investigators will attempt to locate, make contact with, and resume treatment for subjects who fail to complete TB chemoprophylaxis. Primary outcome measures will be the proportion of subjects in each of the three groups who complete the six months of tuberculosis chemoprophylaxis, as well as the mean duration of TB chemoprophylaxis in each group. Primary outcome will be measured by attendance and medication records, urine testing for INH, a medication event monitoring system (MEMS), pill counts, and self-report. Secondary outcome measures will be the proportion of weekly urine tests positive for drugs of abuse, monthly Addiction Severity Index scores, and monthly Risk for AIDS-related Behaviors scores.